#include<stdio.h>

int A[1000001];
int T[1000001];
int N;
long long sum = 1;

int main()
{
	FILE *f = fopen("fractii.in","r");
	FILE *g = fopen("fractii.out","w");
	
	fscanf(f,"%d",&N);
	for(int i=1;i<=N;i++)
		A[i] = i-1;
	for(int i=1;i<=N;i++)
		for(int j=i+i;j<=N;j+=i)
			A[j] -= A[i];
	for(int i=1;i<=N;i++)
		sum += 2*A[i];
	fprintf(g,"%llu",sum);
	
	fclose(g);
	fclose(f);
}